Until Harry gives you a definitive ruling, my opinion would be that the work would be better posted in the 'Other books' section. Many of the e-ink readers have screens the same size as the Sony PRS 500/505 and their owners would be more likely to find it there, and then benefit from your efforts.

I've got a copyright question, Harry. I've downloaded a group of freely distributed PDF's on a number of math topics. Take 'combinatorics', 'topology' or 'analysis' as examples. As long as the authors have allowed the material to be freely distributed (not for profit) may I upload them here?